Thermal decomposition kinetics of poly(trimethylene terephthalate)

Abstract

Poly(trimethylene terephthalate) samples with various molecular weights have been prepared by changing reaction conditions via trans-esterification method. The dynamic thermogravimetric kinetics of these PTT samples under argon, air, and nitrogen were analyzed by Freeman–Carroll, Friedman, and Chang techniques. The effects of molecular weight on the thermostability and the decomposition kinetic parameters of PTT under argon and air were discussed systematically. The effects of atmosphere (air, argon, and nitrogen) were also investigated. The experimental data showed that under argon atmosphere PTT exhibited mainly one decomposition step, and all of the initial degradation temperature, the temperature at the maximum weight-loss rate, the activation energy E, order n and frequency factor Z for decomposition increased with molecular weights. However, under air atmosphere PTT exhibited two main degradation stages. Characteristic temperatures increased but decomposition kinetic parameters decreased with molecular weights for the first decomposition stage. Nevertheless little variation of characteristic temperatures and degradation kinetic parameters has been observed for the second degradation stage. In addition, the decomposition process of PTT (or PET) in argon is similar to that in nitrogen, while much different degradation mechanism can be found in air. In brief, PTT and PET show much lower initial decomposition temperature and degradation-activation energy in air than in nitrogen and argon.